Flotation apparatus



June 21, 1966 F. lsr-:NHARDT ETAL 3,256,987

FLOTATION APPARATUS Filed Oct. 22, 1962 2 SheeiS-Sheet l June 21, 1966 F. lsENHARDT ETAL 3,256,987

FLOTATION APPARATUS Filed Oct. 22, 1962 2 Sheets-Sheet 2 6 F/g. 2 7 I Z I 1;/ i ,Cj f; l2 V12 ing one of the mixtureconstituents.

United States Patent C) s claims. (ci. 209-169) Our invention relates to flotation apparatus for classifying mineral mixtures, available in form of a turbid fluid, by supplying froth-forming air and thereby float- Due to progressing mechanization of mining methods, particularly in coal mines, and 4improving prevention of ily dust underground, there has been a continuing increase in the content of lines, ashes and moisture in the raw coal output. This increasingly requires pre-washing the finest- 'gra-in coal. Hen-ce flotation methods, known for the benefciation of other minerals, are now also being employed for coal dressing to an ever growing extent. This poses the problem of raising the power capacity of existing flotation plants .and providing new flotation equipment of high power rat-ing.

There ,are known flotation apparatus in which the air, required for flotation, is supplied through an air pipe protruding above the level of the particle-laden liquid. The lower end of the air pipe terminates above the supply pipe for the liquid in the lower region of the cell. A stirrer vane or an agitator in form of -an upwardly open running wheel, serves to impart rapid motion to the incoming v liquid and to beat the air into froth-forming bubbles.

It is an object of our invention to augment the eilicacy and eiliciency of the individu-al separator cell, and to improve the transporta-tion of the turbid liquid as well as the intimate mixing of the incoming particle-laden liquid with the inducted air.

To this end, and in accordance with our invention, we produce the froth bubbles `by means of a rotating swirl or -agitator disc in the lower part of the cell which during its rotation also performs a swinging motion, thus oombining an effective beating action with the stirring function. Preferably the agitator disc is mounted to rotate in front of the air supply opening and has its circular edge perform a swinging up and down motion.

According to another, preferred feature of our invention, the swinging disc is mounted on the lower end of an essentially vertical drive shaft, and the plane of the disc extends at an angle differing from 90 so that the disc performs a tumbling motion during its rotation. The tumbling disc is further provided with upwardly protruding agitator ribs on its top side.

According to another feature of our invention, we mount a xed guiding plate above the agitator disc in concentric relation to the drive shaft. and to an -air-supply pipe, the :above-mentioned ribs on top of the agitator disc being equally spaced from the guide plate.

It is preferable, according to a further feature of our invention, to give the ribs of the agitator disc respectively different thickness so as'to attain substantial or approximate balance of the rotating disc. However, such balance may also `be obtained or perfected by adding an unbalance-compensating Weight to the disc, in which case the respective ribs may also be given the same wall thick-v that the turbid liquid, entering into an annular chamberl ice.

of the cell vessel, cooperates with the rotating agitator disc to produce an injector action so that airis inducted through the air-supply pipe.

The agitator disc may be provided with openings, for example uniformlyv arranged bores of circular shape.

For further describing the invention, reference will be had in the following to the embodiment of flotation apparatus according to the invention illustrated by way of example on the accompanying drawings, in which:

FIG. 1 shows 'a flotation cell in lateral view, partly in section.

FIG. 2 shows separately the agitator disc of the same cell on larger scale and in section.

FIG. 3 is a plan view of the agitator disc according to FIG. 2.'

The illustrated flotation cell comprises a tank 1 in which a vertical drive shaft 2 is revolvably journalled. Mounted on the lower end of the shaft 2. near the bottom of the Y vessel is a tumbling disc 3 with upwardly directed ribs 5 uniformly distributed about the hub 4. The plane of the disc 3 is inclined to the axis of the drive shaft -2 so -as to perform a swinging or tumbling motion during rotation. This produces yan intensive mixing of the inducted air with the turbid liquid which is beaten into -a multiplicity of finest bubbles. The upper edges of the rib 5 on disc 3. are spaced at 7 equal amounts from a guiding plate 6 xedly mounted in the vessel closely above the rotatable isc 3.

For substantially balancinlo the rotating disc 3, the vribs 5, having respectively different'heights, are given correspondingly different amounts of thickness so that a substantially balanced and Vibration-free run of the turnbling disc is secured even at high rotating speeds. The 4balance of the disc can be perfected by adding a compensating weight to the bottom side of the disc 3 as shown at 12 in FIG. 3. If desired, the ribs 5 may also be given the same thickness in which case the balancing of the tumbling disc 3 can be effected only by means of an additional weight -attached to .the bottom side of the disc and situated at the same place 12 as shown in FIG. 3, exept that in the latter case the corrective weight must be arger.

For passing air into the cell vessel 1, an air pipe 9, 9' coaxially surrounding the drive shaft 2, has its lower portion 9 extend downwardly close to the guiding plate 6 with the exception of a small annular gap 1d. As a result, the turbid bath arriving through an inlet duct 11 and a horizontal supply pipe 8 in an annular channel 8 around the gap 10, imposes a forceful injector action upon the air supply pipe 9. This affords the assurance that air is continuously inducted through the air supply pipe.V Due to the forceful motion which the tumbling disc 3 imparts to the turbid bath, particularly in the multitude of eddies occurring at the perimeter of the disc, the air is beaten into finest froth bubbles which become enriched with the mineral particles of the bath to be floated away, thus achieving a high-yield of the flotation cell. The floated material, such as coal fines, enveloped in the ascending froth Ibubbles, collects on the bath surface from which the lines-containing froth is mechanically stripped away to flow laterally over the top edge of the cell tank. The underflow, containing essentially only the gangue or waste, passes through an outlet opening 15 and aduct 16 upwardly whence it flows over the top of an overflow gate 17 of adjustable height and through a duct 18 into an outlet conduit 19.

The above-mentioned stationary guide plate 6 is preferably provided with uniformly distributed guiding vanes 6 and is rigidly mounted on a supporting'structure 12 engaged by the air supply pipe 9 and' joined or integral with the bath supply structure 8. The shaft 2 is driven by means of a belt drive 13 on top of the vessel structure from an electric motor 14.

In contrast to the agitator wheels of known otation cells, a otation apparatus according to the invention has the advantage that, by virtue of the to and fro motion of the swinging disc simultaneous with its rotation,

a considerably more forceful motion is imparted to the turbid bath, thus producing a more intensive and more stable air-bubble formation. As a result, the efficacy and output of the cell for given dimensions is considerably increased. In addition, the swinging disc promotes the supply of air and secures a continuous induction of the air needed for ample froth formation and reliable flotation.

Upon a study of this disclosure it will be obvious to those Skil-led in the art that with respect to structural details or arrangement and number of components, our invention permits of various modifications and can be given embodiments other than particularly illustrated and described herein, without departing from the essential features of the invention and within the scope of the claims annexed hereto.

We claim:

1. An apparatus for air-froth dotation, comprising a vessel for liquid medium, a iixed tubular air-suction duct extending downwardly into said vessel and having a lower open end whose outlet opening is located in the bottom portion of said vessel, a vertical drive shaft coaxially traversing said air duct and protruding downwardly out of said opening, said shaft having a smaller diameter than said duct to form an annular suction space together therewith, liquid-supply means having an end portion surrounding and radially spaced from the lower end of said air duct and having an outlet opening of greater diameter than the diameter of said air duct outlet opening and annularly surrounding the outlet opening of said air duct, and a stirrer disc mounted on said shaft below said openings and rotatable for producing a flow of liquid in said liquid-supply means downwardly and outwardly along and around said open air duct end whereby air is.-

injected into said liquid through said air duct.

2. A flotation apparatus for classifying mineral mixtures in liquid media by air-froth tioating a constituent of the mixture, comprising a vessel containing mixtureladen liquid when the apparat-us is in operation, and having an overflow for separated materials, a tubular airlsuction duct extending downwardly into said vessel, said tube having an open lower end whose outlet opening is located in the bottom portion of said vessel, a vertical drive shaft coaxially traversing said air duct and having a lower end protruding downwardly out of said air outlet opening, a horizontal guide plate tixedly mounted in said vessel near said opening and having a suction opening greater in diameter than, directly below and radially spaced from said air outlet opening, a liquid supply structure having an end portion forming an annular chamber coaxially around said lower end of said air duct near said air outlet opening and above Vsaid plate and cornmunicating with said suction opening, and a stirrer member mounted on said shaft below said air outlet opening and said suction opening and rotatable for producing a flow of liquid in said liquid-supply structure downwardly and outwardly along and around said lower open end of said air duct whereby air is injected into said liquid through said air duct.

3. An apparatus for air-froth flotation, comprising a vessel for liquid medium, a xed tubular air-suction duct extending downwardly into said vessel and having a lower open end whose outlet opening is located in the bottom portion of said vessel, a vertical drive shaft coaxially traversing said air duct and protruding downwardly out of said opening, said shaft having a smaller diameter than said duct to form an annular suction space together therewith, a liquid-supply duct having an end portion coaxially aligned with, surrounding and radially spaced from the lower end of said air duct, and dening a liquid flow path extending in the same flow direction as said air duct end, said liquid-supply duct having an outlet opening adjacent and annularly surrounding the outlet opening of said air duct, said liquid-supply duct outlet opening having a greater diameter than the diameter of said air duct outlet opening, and a stirrer disc mounted on said shaft below said outlet openings and rotatable for producing a flow of liquid in said liquid-supply duct end portion downwardly and outwardly along and around said open air duct end whereby air is injected into said liquid through said air duct.

4. In flotation apparatus according to claim 3, said disc having upwardly protruding ribs distributed on the top side of said disc, said ribs having respectively ditferent heights and having respective top edges at `substantially the same height of said shaft, and said ribs of greater height having correspondingly smaller thickness magnitudes than said ribs of lesser height so as to substantially balance said disc.

5. An apparatus for air-froth flotation, comprising a vessel for liquid medium, a xed tubular air-suction duct extending downwardly into said vessel and having a lower open end 'whose outlet opening is located in the bottom portion of said vessel, a vertical drive shaft coaxially traversing said air duct and protruding downwardly out of said opening, said shaft having a smaller diameter than said duct to form an annular suction space together therewith, a liquid-supply duct having an end portion coaxially aligned with, surrounding and radially spaced from the lower end of said air duct, and defining a liquid ow path extending in the same flow direction as said air duct end, said liquid-supply duct having an outlet opening adjacent and annularly surrounding the outlet opening of said air duct, said liquid-supply duct outlet opening having a greater diameter than the diameter of said air duct outlet opening, and a stirrer disc mounted on said shaft below said outlet openings and rotatable for producing a How of liquid in said liquidsupply duct end portion downwardly and outwardly along and around said open air duct end whereby air is injected into said liquid through said air duct, said disc being inclined to the axis of said shaft for performing a turnbling motion when rotated and having a plurality of peripherally distributed ribs on the top face thereof, and a guiding Aplate mounted in fixed relation to the open end portion of said liquid-supply duct and extending in a substantially horizontal plane above said disc, said ribs having respective' top dges spaced substantially equally from said guiding plate.

References Cited by the Examiner UNITED STATES PATENTS 1,470,607 10/1923 Hazell 103-115 1,654,907 1/1928 Wood 103-115 X 1,908,002 5/1933 Valentine 259-96 2,031,590 2/1936 Daman 261-93 2,316,770 4/1943 Daman 209-169 2,336,798 12/1943 Nash.

2,393,976 2/1946 Daman et al 209-169 2,423,456 7/ 1947 Logue 209-164 2,682,576 6/1954 Frank ID3-111.1 X 2,711,823 6/1955 Kihlstedt et al. 209-169 2,875,897 3/1959 Booth 209-169 2,944,802 7/ 1960 Daman 209-169 X HARRY B. THORNTON, Primary Examiner.

ROBERT F. BURNETT, Examiner.

R. HALPER, K. V. ROCKEY, Assistant Examiners. 

2. A FLOTATION APPARATUS FOR CLASSIFYING MINERAL MIXTURES IN LIQUID MEDIA BY AIR-FROTH FLOATING A CONSTITUENT OF THE MIXTURE, COMPRISING A VESSEL CONTAINING MIXTURELADEN LIQUID WHEN THE APPARATUS IS IN OPERATION, AND HAVING AN OVERFLOW FOR SEPARATED MATERIALS, A TUBULAR AIRSUCTION DUCT EXTENDING DOWNWARDLY INTO SAID VESSEL, SAID TUBE HAVING AN OPEN LOWER END WHOSE OUTLET OPENING IS LOCATED IN THE BOTTOM PORTION OF SAID VESSEL, A VERTICAL DRIVE SHAFT COAXIALLY TRAVERSING SAID AIR DUCT AND HAVING A LOWER END PROTRUDING DOWNWARDLY OUT OF SAID AIR OUTLET OPENING, A HORIZONTAL GUIDE PLATE FIXEDLY MOUNTED IN SAID VESSEL NEAR AND OPENING AND HAVING A SUCTION OPENING GREATER IN DIAMETER THAN, DIRECTLY BELOW AND RADIALLY SPACED FROM SAID AIR OUTLET OPENING, A LIQUID SUPPLY STRUCTURE HAVING AN END PORTION FORMING AN ANNULAR CHAMBER COAXIALLY AROUND SAID LOWER END OF SAID AIR DUCT NEAR SAID AIR OUTLET OPENING AND ABOVE SAID PLATE AND COMMUNICATING WITH SAID SUCTION OPENING, AND STIRRER MEMBER MOUNTED ON SAID SHAFT BELOW SAID AIR OUTLET OPENING AND SAID SUCTION OPENING AND ROTATABLE FOR PRODUCING A FLOW OF LIQUID IN SAID LIQUID-SUPPLY STRUCTURE DOWNWARDLY AND OUTWARDLY ALONG AND AROUND SAID LOWER OPEN END OF SAID AIR DUCT WHEREBY AIR IS INJECTED INTO SAID LIQUID THROUGH SAID AIR DUCT. 